As integrated circuit manufacturing technology has advanced, it has become possible to decrease the size of a wide variety of electronic devices. Great efforts have successfully been directed toward the miniaturization of telecommunication devices because of the advantages of making such devices easily portable. Portable radio transceivers can provide communication capabilities in a wide variety of circumstances where conventional landline communication is unavailable, impractical or inconvenient. Personal radio transceivers are used to establish communication links into areas of rugged terrain which are inaccessible by conventional telephone landlines, to provide constant, private communication between two or more individuals without the inconvenience of dialing and answering a telephone, and to provide communication capabilities to an individual who must communicate while moving (e.g. while walking or travelling in a moving vehicle) or while at fixed positions distant from conventional landline communication devices.
Personal radio transceiver components have recently become so miniaturized that a very complex transceiver having great communication and functional capabilities may be packaged in a case small enough to be easily carried in the hand or hung from a belt. The transceiver case can be made impact-resistant and waterproof so that the transceiver will function after rough treatment (such as dropping, bumping against objects, exposure to the elements, etc.). Personal transceivers of high reliability and durability are thus possible.
One of the limitations on the reliability and durability of personal radio tranceivers at present is the construction and design of the control surface (user interface). Early personal transceivers had relatively unsophisticated electronics and associated functions, and usually operated on only one or a small number of fixed, predetermined frequencies. The only user controls often provided on such early transceivers were simple power on/off and transmit/receive switches, a receiver volume control knob, and perhaps a switch or knob to select one of a small number of crystal-controlled operating frequencies.
As integrated circuit technology has advanced, the sophistication of the functional capabilities of personal transceivers has increased dramatically. Modern personal transceivers normally are capable of a wide variety of functions, such as fully programmable operating frequencies (within a band of frequencies), programmable semi-duplex frequency operation (whereby the receive frequency of the transceiver may be selectively offset a programmable frequency difference from the transmit frequency), selectable power output, receiver scanning capability (whereby the receiver automatically continuously searches a number of programmed frequencies or the frequency spectrum at programmable intervals between two programmable frequencies to locate active channels, and may either stop scanning when an active frequency is found, or continue scanning and store the active frequency in an internal memory for later reference), memory capabilities (whereby last-used frequencies of operation may be stored or whereby a random access memory may be programmed with a number of commonly-used frequencies to allow a user to choose the frequency of operation without having to reprogram the frequency in full each time it is to be used), tone encoding (whereby the transceiver can transmit a series of user-selected tones for accessing private receivers, for controlling devices interfaced with receivers, or for accessing standard TOUCH-TONE.RTM. telephone lines through a base transceiver connected to a "phone patch"), selectable transmitter modulation modes and levels, etc.
As the functional capabilities of personal transceivers have increased, suitable interface devices for enabling a user to interact with highly complex transceivers to program the transceiver functions have become necessary. A suitable control interface must necessarily have a high control per unit area density because of the limited exterior surface area of the case of the personal transceiver. The interface must also be durable, shock-resistant, weather resistant and highly reliable under a variety of adverse conditions in order to withstand the rough treatment to which personal transceivers are subjected without degrading the reliability of the transceiver. The cases of personal transceivers conventionally are long, thin rectangular boxes (so that the transceiver can be easily held in the hand), where one of the ends of the box conventionally serves as a bottom upon which the transceiver may rest. It is desirable to position the entire user interface on the top end of the rectanglar transceiver case so that the controls are readily accessible when the transceiver is resting on its bottom, inserted into a leather or vinyl case hung from a belt, or temporarily housed in a battery charger or a "slide-mount"-type receptacle in a vehicle.
Matrix alphanumeric keyboards are especially suited for personal transceiver control interfaces because they provide high control density per unit area, are useful for programming a variety of different types of information, and are compatible with standard telephone TOUCH-TONE.RTM. pad configurations. Moreover, much of the programming information needed to program a personal transceiver is numeric (or can be reduced to numerics). While conventional telephone-type TOUCH-TONE.RTM. pads such as those disclosed by Adams et al (U.S. Pat. No. 4,291,202 issued Sept. 22, 1981), Demler et al (U.S. Pat. No. 3,982,081 issued Sept. 21, 1976), Scheingold et al (U.S. Pat. No. 3,909,564 issued Sept. 30, 1975) and Ueda et al (U.S. Pat. No. 4,153,822 issued May 8, 1979) provide high reliability and durability, they are much too large to be positioned on the top surface of conventional personal radio transceivers.
Such conventional TOUCH-TONE.RTM. pads have been used in the past for device user control interfaces (including personal radio transceiver control surfaces) by mounting them on one of the elongated sides of the rectangular case of the device. For example, Ueda et al (mentioned above) discloses a TOUCH-TONE.RTM. dial plate mounted on the back of a substantially rectangular telephone handset. See also Adams et al. However, this mounting position is undesirable for personal transceiver applications because it subjects the dial plate to accidental operation and possible damage from impact when the rectangular case is bumped into objects. Moreover, a personal radio tranceiver must be picked up and held in the hand or rested horizontally on its back (usually an inconvenient position because the transceiver antenna must normally be maintained in a vertical position since VHF transmissions are conventionally vertically-polarized) in order to operate a control surface so positioned. A control surface mounted on a side surface of a personal radio transceiver is also difficult or impossible to operate when the transceiver is hung from a belt, and "slide-mount"-type receptacles must be adapted to provide openings or spaces to accommodate a control surface so positioned.
Even if known TOUCH-TONE.RTM. pads could be sufficiently minaturized to be mounted on the top end of the rectangular personal transceiver case, they would not be sufficiently weather-resistant to avoid degradation of transceiver reliability. Moreover, a highly reliable way of connecting the TOUCH-TONE pad to the remainder of the transceiver electronics while providing for easy assembly and disassembly, mechanical shock isolation, and rf shielding would be necessary.